I have a Juki 98Q and have quilted up to a 92" square quilt...you can see some of my quilts in my photo album here. I did not have room for a longarm, and not enough money for one even if I did. I took the plunge and bought the Juki without ever trying then out...just read on a forum. I could not believe the difference that added space made. I had quilted quilts on my regular Pfaff and my Viking, and would always swear off ever trying it again. And that was even with the bigger baby quilts I make. Now, I actually look forward to the quilting.
But if I had room for a long arm, or mid arm, I would read all I could and test drive all I could, and make my decision from there. I think there is a longarm yahoo group...you might learn a lot there.